Apparatus for fabricating a preform

ABSTRACT

The present invention is a highly predictable composite usable to fabricate such structural articles as complex-shaped automotive body parts and building panels. Included in this composite is at least one netlike preform having a plurality of inter-crossed roving bound to each other at thermoset junction points. This preform is compressed into a mold, and at least one layer of polymer paste is added thereto. The preform layers and the polymer paste layers are compressed to the shape of the mold, and then they are heat and flame treated to complete the curing of the thermoset resin and to produce a desired surface finish.

This application is a division of application Ser. No. 08/232,992 filedon Apr. 25, 1994 and now U.S. Pat. No. 5,595,795.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel composite and a method andapparatus for manufacturing the same. Specifically, the composite ofthis invention includes a reinforcing preform having a plurality ofinter-crossing strands or roving arranged to form a plurality ofjunction points. The crossing strands or roving at each of thesejunction points are connected to each other by a thermoset bindingmaterial.

2. Description of the Prior Art

Reinforced polymer based composites, and methods for making the same,are well known in the prior art. U.S. Pat. No. 3,535,180 issued to GlenP. Gasaway on Oct. 20, 1970, discloses a plastic sheeting having areinforcing layer disposed between two plastic plates. The reinforcinglayer is an internal network fabricated from traversing two sets ofequally spaced, parallel glass strands. A thermoplastic bonding materialis utilized at the points of intersection of the traversing strands.This bonding material fuses the strands together to promote thestability and strength of the network. The melting point of the bondingmaterial is less than the melting point of the glass strands. Therefore,the bonding material can be coated onto the glass strands withoutdetrimentally affecting the integrity of the glass strands. Likewise,the melting point of the plastic plates is less than the melting pointof the bonding material, thus permitting the plastic plates to be coatedonto the reinforcing network.

U.S. Pat. No. 3,222,237 issued to William R. McKelvy on Dec. 7, 1965,illustrates a unitary plastic sheet having centrally imbedded therein areinforcing mesh of traversing fibers. One preferred method offabricating this sheet includes placing a non-woven network of glassscrim or the like between a polyethylene sheet and a film ofsubstantially molten polyethylene. The outer surface of the moltenpolyethylene film is gradually cooled. As this outer surface cools, themolten center of the film flows through the mesh and fuses with thepolyethylene sheet. After continued cooling, a highly flexible solid isformed almost entirely about the reinforcing mesh.

Other patents relating to reinforcing layers for polymer basedcomposites are disclosed in U.S. Pat. No. 3,272,645 issued to MarcelDuhoo, et al. on Sep. 13, 1966, and U.S. Pat. No. 3,444,025 issued toKenneth M. Hillas on May 13, 1969. The Duhoo, et al. patent shows aflexible laminated sheet material fabricated by coating a web of wovenor non-woven material with a non-adhesive gel of thermoplastic orthermosetting material. The coated webs of this invention can be stackedupon each other and then deeply molded under heat and pressure. TheHillas patent discloses a bonded, non-woven scrim produced from twolayers of essentially parallel spaced-apart strands and a layer ofthermoplastic resin. This layer of thermoplastic resin is heated at atemperature above its melting temperature until it deforms under its ownweight and collapses so as to surround the strands of the scrim. Theentire structure is then cooled until the thermoplastic resin returns toa solid state.

None of the above inventions and patents, taken either singly or incombination, is seen to describe the instant invention as claimed.

SUMMARY OF THE INVENTION

The present invention relates to a novel composite and a method andapparatus for manufacturing the same. Specifically, the composite ofthis invention includes a reinforcing preform having a plurality ofinter-crossing strands or roving arranged to form a plurality ofjunction points. The crossing roving at each of these junction pointsare connected to each other by a thermoset binding material, which ispermitted to permeate the roving at each of the junction points. Thisthermoset binding material solidifies within each junction point to bondthe crossing roving together.

After the preform has been fabricated, a desired amount is cut from themanufactured roll of the preform and is placed into a mold. Polymerlayers may be added to the preform and the entire structure may be curedby heat treating. One method of combining the preform with one or morepolymer layers is to place a first polymer layer into the female portionof a mold. This layer is compressed to the shape of the mold, and thepreform is then placed onto the first polymer layer. The preform andthis first polymer layer are then compressed, and a second polymer layeris placed upon the preform. Again the contents of the mold arecompressed, and the process is repeated for any additional layers.Subsequent to compressing the last layer, the mold is closed andsuitably compressed. The resultant structure is then heat treated tocomplete the curing process and to produce a low profile surface finish.

Accordingly, it is a principal object of the invention to provide anovel preform having a plurality of thermoset junction points.

It is another object of the invention to provide a novel compositehaving at least one preform with at least one polymer layer securedthereto.

It is a further object of the invention to provide a novel method forfabricating a composite.

Still another object of the invention is to provide novel apparatus formanufacturing a preform and composite.

It is an object of the invention to provide improved elements andarrangements thereof in an apparatus for the purposes described which isinexpensive, dependable and fully effective in accomplishing itsintended purposes.

These and other objects of the present invention will become readilyapparent upon further review of the following specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the preform of the invention.

FIG. 2 is a front elevational view in cross section of the preform ofFIG. 1.

FIG. 3 is a top plan view of the preform of FIG. 1, showing the preformin a complex shape.

FIG. 4 is a side elevational view of an apparatus for manufacturing thepreform of the invention.

FIG. 5 is a top plan view of the apparatus of FIG. 4.

FIG. 6 is an enlarged, partial perspective view of the container of theapparatus of FIG. 4.

FIG. 7 is an enlarged, top plan view of the processing surface of theapparatus of FIG. 4.

FIG. 8 is an enlarged, partial front elevational view of the cuttingmechanism of the apparatus of FIG. 4.

FIG. 9 is an enlarged, partially exploded, side elevational view of themold of the present invention.

FIG. 10 is an enlarged, side elevational view of the mold of FIG. 9.

FIG. 11 is a side elevational view of an apparatus for deliveringworkpieces of the present invention to a mold.

FIG. 12 is a front elevational view in cross section of the apparatus ofFIG. 11.

FIG. 13 is a front elevational view in cross section of one workpiecereleasing station of the apparatus of FIG. 11.

Similar reference characters denote corresponding features consistentlythroughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is a composite for fabricating such articles asautomotive body parts and building panels. This composite isinexpensive, easy to manufacture, and is especially well suited forfabrication into structural articles of a complex shape. The compositeincludes at least one layer of a highly permeable reinforcing preform 10and at least one layer of a hybrid polymer paste.

As illustrated in FIG. 1, reinforcing preform 10 includes a transverseset of equally spaced and parallel strands or roving 12. These strandsor roving 12 traverse a longitudinal set of equally spaced and parallelstrands or roving 14 to create a plurality of junction points 16. Thecrossing strands or roving at each of these junction points 16 are heldtogether by a thermoset bonding material, deposited onto the junctionpoint and permitted to permeate therethrough. As a roving is anaggregate of strands, roving will be utilized hereafter to refer toeither a strand or a roving.

Prior to application upon the junction points 16, the liquid thermosetbinding material is stored within a vacuum sealed container. Included inthis liquid thermoset binding material are appropriate chemicalcatalysts, inhibitors and accelerators for inducing the liquid materialto gradually solidify upon exposure to air. When the liquid thermosetbinding material is released onto a junction point 16, it permeatesthrough the junction point 16, and solidifies therein. The solidifiedmaterial rigidly connects each pair of crossing roving.

As illustrated in FIG. 1, preform 10 is fabricated to have a substantialdistance between adjacent thermoset junction points 16. This substantialdistance assures that preform 10 is extremely permeable to moltenpolymers. When a molten polymer layer is placed onto one side of preform10, it flows through the permeable preform 10 and fuses with a polymerlayer on the opposing side of preform 10. Upon returning the polymer toa solid state, the result is an exceptionally strong, reinforcedcomposite.

In addition to assuring permeability of preform 10, the substantialdistance between adjacent junction points 16 promotes flexibility ofpreform 10. As depicted in FIG. 3, preform 10 is readily adjustable intocomplex shapes. This adjustability arises from the uninhibited movementof the portions of the roving 12,14 intermediate to junction points 16.These portions can bend or flex without engaging neighboring roving. Forpreforms fabricated with either closely or randomly spaced roving, thereis a likelihood that movement of the roving will be inhibited byadjacent roving, thus hindering the ability of the preform to assume acomplex shape.

Although a preform having a woven configuration is within the scope ofthis invention, the preferred embodiment is a layered arrangement, wheretransverse roving 12 form a first layer, and longitudinal roving 14 forma second layer. As with the spacial arrangement of roving 12,14, thislinear arrangement aids in promoting flexibility of the preform. In suchan arrangement, roving 12,14 are substantially stress free and thereforeeasily manipulated into complex shapes. In contrast, the roving of awoven configuration are held under both tension and compression forcesprior to attempted manipulation into a complex shape. These tension andcompression forces restrict the roving flexibility by opposing itsmovement into a complex shape. The layered arrangement of roving 12,14is also preferable because it is easily and accurately modelled foranalysis. The linear arrangement of roving 12,14 is two dimensional, andtherefore may be evaluated by two dimensional analysis. A wovenconfiguration, on the other hand, must be modelled by an intricate threedimensional analysis, which is both time consuming and costly.

Although transverse roving 12 can be arranged to cross longitudinalroving 14 at any angle, it is preferable that such an angle isapproximately 90 degrees. This arrangement creates a net-like structurehaving either rectangular or square openings within which molten polymeror polymer paste flows prior to solidifying by cooling or curing. Havingthe preform architecture forming rectangular or square openings createsa more predictable compound than that which results from a preformhaving arbitrary quadrilateral openings formed by strands crossing eachother at angles other than 90 degrees.

As shown in FIG. 2, each thermoset junction point 16 includes an amountof thermoset binding material 18 that did not permeate into roving12,14, but rather solidified upon the upper most portion of transverseroving 12. Additionally, each thermoset junction point 16 includes anamount of thermoset binding material 20 that permeated completelythrough roving 12,14 and solidified upon the lower most portion oflongitudinal roving 14. Assuming the composition of roving 12,14 isknown, it is possible to control the amount of thermoset bondingmaterial that solidifies on both the upper most portion of transverseroving 12 and on the lower most portion of longitudinal roving 14. Thisis accomplished by adjusting the consistency of the thermoset bindingmaterial and also by adjusting the inhibitors and accelerators mixedtherein.

Adjusting the amount of material on either the upper most portion oftransverse roving 12 or on the lower most portion of longitudinal roving14 enables the manufacturer of preform 10 to control the height of thematerial 18,20 in relation to roving 12,14 respectively. Hence, it ispossible to control the minimum distance between preform 10 and a moldwithin which preform 10 may be placed. Additionally, if preform 10 isutilized in a composition containing a number of adjacently arrangedpreforms, the minimum distance between each preform can be controlled.As different intervals between adjacent preforms correspond to varyingstructural characteristics, the manufacturer can fabricate the preformto match his or her particular needs.

The material utilized for roving 12,14 can be any fiber capable of beingformed into an elongated, continuous roving. Suitable materials areinorganic fibers, such as fiberglass, and organic fibers, such as aramidfibers. These fibers exhibit characteristics of both flexibility anddurability. Any thermoset material that can be appropriately maintainedin a liquid state can be utilized to bind the traversing roving at thejunction points. One preferable material for this thermoset binder isunsaturated polyester resin mixed with standard catalysts, inhibitorsand accelerators.

After the junction points 16 of preform 10 are bonded with the thermosetmaterial, the composite is fabricated by placing preform 10 between twopolymer paste layers and then compressing and heat treating thecombination so that the polymer paste layers bond to each other at theopen areas of the preform. If desired, composites could include anynumber of preforms 10, and any number of polymer paste layers.

One method for manufacturing a composite according to the invention isto place a first polymer paste layer into the female portion of a mold.The first polymer paste layer is then compressed so that it conforms tothe shape of the mold. The preform 10 is then placed into the femaleportion of the mold, onto the polymer paste layer already positionedtherein. The contents of the mold (preform and first polymer pastelayer) are then compressed into the mold in a similar manner as thefirst polymer paste layer. A second polymer paste layer is then placedinto the female portion of the mold, onto the preform. Again thecontents of the mold are compressed. This process is repeated if it isdesired to include additional layers of either preform or polymer paste,or both. A slight variation of this method is to heat the female portionof the mold prior to including each polymer layer therein. Thetemperature to which the mold should be heated is that temperaturesufficient to permit the polymer to assume the shape of the mold, butthat is not elevated to the point where the consistency of the polymermakes it difficult to place additional layers thereon.

If desired, inserts and sandwich holes can be incorporated into thecomposite. An insert is any device that is to be rigidly secured by thepolymer layers. Sandwiched holes are gaps in the polymer layers thatincrease the flexural capabilities of the composite. These holes can befabricated by placing such articles as a blow molded container into oneor more of the polymer layers. Such a hole must be positioned betweentwo layers of preform 10, which carry the load when the composite isdeformed.

Subsequent to compressing the final layer into the mold, the maleportion of the mold is tightly secured to the female portion. The closedmold is then suitably compressed within a molding press or similardevice, and then the formed part is removed from the mold. This formedpart is then heat and flame treated to complete the curing of thethermosetting material and to produce a desired surface finish.

The manufacture of the composite is not limited to the above describedmethod. Rather, preform 10 can be placed within an injection mold, andthen surrounded by a thermoplastic polymer melt. The contents of themold are then cooled to enable the polymer melt to solidify, and theformed composite part is then removed from the mold.

Another method for manufacturing the composite includes placing preform10 and at least two monomers into a reaction injection mold, where themonomers simultaneously polymerize and fill up the mold cavity. Stillanother method of manufacturing the composite is to place preform 10within a molten metal injection mold, and then inject therein moltenmetal to surround preform 10. Further still, preform 10 can be placedwithin a thermoset resin transfer mold and then surrounded by thermosetpolymer resin.

In FIGS. 4 and 5, there is illustrated an apparatus 22 for manufacturingpreform 10. This apparatus 22 includes a support table 24 having aprocessing surface 26 upon which the longitudinal roving 14 and thetransverse roving 12 are arranged prior to bonding the respectivejunction points 16. Longitudinal roving 14 are the first roving to beplaced upon processing surface 26. These roving 14 are released from thelongitudinal creel 28 and then pulled across processing surface 26 bythe motorized spindle 30. Longitudinal creel 28 includes appropriateguides 32 for placing roving 14 upon processing surface 26.

After longitudinal roving 14 have been arranged upon processing surface26, the transverse roving 12 are positioned so as to cross overlongitudinal roving 14. These transverse roving 12 are released from thesliding creel 34, which includes a set of guides 36 for placing roving12. The clamp 38 secures one end of transverse roving 12, while slidingcreel 34 moves along member 40 and releases transverse roving 12 ontolongitudinal roving 14. In FIG. 5, sliding creel 34 is illustrated in aposition subsequent to releasing transverse roving 14.

The robot arm 42 supports the vacuum sealed container 44 which, as shownin FIG. 6, includes a plurality of syringes 46. The thermoset bindingmaterial is stored in container 44, and is released through syringes 46,onto the junction points 16. Included within processing surface 26 is aplurality of openings 48 upon which the junction points 16 arepositioned prior to application of the binding material. These openings48, which are illustrated in FIG. 7, prevent the thermoset bindingmaterial from adhering to processing surface 26 should this materialcompletely permeate through the junction point 16 to which it wasapplied. This permits for easy advancement of preform 10 onto spindle30, and also allows the thermoset binding material to appropriatelysolidify onto the lower most portions of longitudinal roving 14, asdiscussed above.

After a portion of the preform has been formed, it is rolled uponspindle 30 for storage. Prior to this rolling, the cutting mechanism 50severs transverse roving 14 from transverse creel 34. As depicted inFIG. 8, this cutting mechanism 50 includes a motor 52 for controllingboth the rotational and longitudinal movement of the cutting wheel 54.This motor 52 causes gear 56 to rotate, which in turn causes shaft 58 torotate. This rotation of shaft 58 also rotates both the cutting wheel 54and the spur gear 60. As spur gear 60 rotates, it travels upon the rackgear 62 and carries the entire cutting mechanism 50 longitudinally alongthe length of processing surface 26. Annular bearings or rings 64 arepositioned between the upper and lower surfaces 65,66, and facilitatemovement of the shaft 57 therethrough. Both surfaces 65,66 act as aguide for the annular bearings 64, with the lower surface 66 beingaffixed to bearing plate 67, which is in turn affixed to the table 24.

Once manufacture of preform 10 is complete, a desired amount of preform10 can be cut from a manufactured roll of preform 10. The polymer layerscan be added to the preform 10, and the entire structure can be moldedas hereinabove described. A typical method of molding the structure isillustrated in FIG. 9. Here, the first polymer layer 68 and preform 10are shown to be in the shape of the female mold 70, which is sittingupon table 71. These layers 68,10 have been compressed by the maleportion 72 of the mold. That the layers 68,10 are spaced from the mold70 is for illustrative purposes only, and obviously, during the additionof new layers 74, the already compressed layers 68,10 remain in thefemale portion 70 of the mold.

The second polymer layer 74 is illustrated to be substantially flat innature. This layer 74 has not yet been compressed by male portion 72.When layer 74 is placed upon preform 10, the robot arm 76 moves the maleportion 72 to compress the contents within female portion 70, and thestructure of FIG. 10 is formed. This structure is then furthercompressed and heat treated, as necessary. In FIG. 10, the layers68,10,74 are shown to be spaced from each other for illustrativepurposes only.

The apparatus 78 depicted in FIGS. 11 and 12 is utilized to deliverlayers 68,10,74 to female portion 70 of the mold. Although apparatus 78is shown to include three workpiece releasing stations 80,82,84, thenumber of releasing stations could vary depending upon the number oflayers to be added to female portion 70. As shown in FIG. 12, the robotarm 86 locates apparatus 78 above female portion 70, so one of thelayers held at the stations 80,82,84 can be received therein. After oneof these layers 68,10 or 74 has been released into the mold 70, robotarm 86 moves apparatus 78 away from mold 70, and male portion 72compresses the contents of the mold.

Each of the workpiece releasing stations 80,82,84 are independentlypowered, and each includes a pair of plates 88,90, capable of separatingfrom each other to release the workpiece stored thereon. Each of theseparable plates 88,90 is attached to a support 92,94, and is movableinside a guide 96. As shown in FIG. 13, which is taken along line 13--13of FIG. 11, a pulley mechanism controls movement of supports 92,94within guides 96. This pulley mechanism includes an assortment ofpulleys 98 having a cable 100 arranged thereon. Each of the supports92,94 is connected to cable 100 such that clockwise rotation of the mainpulley 102 separates plates 88,90 from each other, and counter clockwiserotation of main pulley 102 draws plates 88,90 closer to each other. InFIG. 12, plates 88,90 of the workpiece releasing station 84 areseparated from each other, and the plates of workpiece releasingstations 80,82 are proximate to each other. After the workpiece has beenreleased from station 84, arm 86 carries the apparatus away from mold70, and permits compression arm 72 to engage the mold. Compression arm72 travels away from mold 70, and arm 86 carries apparatus 78 back tomold 70, where the next workpiece can be released. This processcontinues until the plates of the upper most station have separated andreleased the workpiece initially held thereon.

It is to be understood that the present invention is not limited to thesole embodiment described above, but encompasses any and all embodimentswithin the scope of the following claims.

I claim:
 1. An apparatus for fabricating a preform of intersectinglongitudinal roving and transverse roving, said apparatus comprising:aprocessing surface configured to define a plurality of openings therein;a first set of guides for placing said longitudinal roving upon saidprocessing surface; a second set of guides for placing said transverseroving upon said longitudinal roving, thereby creating a plurality ofjunction points; means for aligning at least one of said junction pointswith at least one of said openings to form at least one aligned junctionpoint; and means for depositing a binding material upon said at leastone junction point.
 2. The apparatus according to claim 1, wherein saidmeans for depositing includes a movable arm having at least one syringeattached thereto, said binding material being deposited from said atleast one syringe.
 3. The apparatus according to claim 1, furthercomprising a cutting mechanism movably attached to said processingtable, said cutting mechanism for severing said transverse roving.